// SPDX-License-Identifier: GPL-2.0
/*
 * upatch-manage
 * Copyright (C) 2024 Huawei Technologies Co., Ltd.
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along
 * with this program; if not, write to the Free Software Foundation, Inc.,
 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
 */

#ifndef _LINUX_LIST_H
#define _LINUX_LIST_H

#include <stddef.h>

/*
 * Simple doubly linked list implementation.
 *
 * Some of the internal functions ("__xxx") are useful when
 * manipulating whole lists rather than single entries, as
 * sometimes we already know the next/prev entries and we can
 * generate better code by using them directly rather than
 * using the generic single-entry routines.
 */

#define container_of(ptr, type, member) \
    ((type *)(((void *)(ptr)) - offsetof(type, member)))

struct list_head {
    struct list_head *next, *prev;
};

#define LIST_HEAD_INIT(name) \
    { \
        &(name), &(name) \
    }

#define LIST_HEAD(name) struct list_head name = LIST_HEAD_INIT(name)

#define INIT_LIST_HEAD(ptr) \
    do { \
        (ptr)->next = (ptr); \
        (ptr)->prev = (ptr); \
    } while (0)

static inline void list_init(struct list_head *list)
{
    list->next = list;
    list->prev = list;
}

/*
 * Insert a new entry between two known consecutive entries.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_add(struct list_head *new, struct list_head *prev,
    struct list_head *next)
{
    next->prev = new;
    new->next = next;
    new->prev = prev;
    prev->next = new;
}

/**
 * list_add_head - add a new entry
 * @new: new entry to be added
 * @head: list head to add it before
 *
 * Insert a new entry before the specified head.
 * This is useful for implementing queues.
 */
static inline void list_add_head(struct list_head *new, struct list_head *head)
{
    __list_add(new, head, head->next);
}

/**
 * list_add - add a new entry
 * @new: new entry to be added
 * @head: list head to add it after
 *
 * Insert a new entry after the specified head.
 * This is good for implementing stacks.
 */
static inline void list_add(struct list_head *new, struct list_head *head)
{
    __list_add(new, head->prev, head);
}

/*
 * Delete a list entry by making the prev/next entries
 * point to each other.
 *
 * This is only for internal list manipulation where we know
 * the prev/next entries already!
 */
static inline void __list_del(struct list_head *prev, struct list_head *next)
{
    next->prev = prev;
    prev->next = next;
}

/**
 * list_del - deletes entry from list.
 * @entry: the element to delete from the list.
 * Note: list_empty() on entry does not return true after this, the entry is
 * in an undefined state.
 */
static inline void __list_del_entry(struct list_head *entry)
{
    __list_del(entry->prev, entry->next);
}

static inline void list_del(struct list_head *entry)
{
    __list_del_entry(entry);
}

/**
 * list_replace - replace old entry by new one
 * @old: the element to be replaced
 * @new: the new element to insert
 *
 * If @old was empty, it will be overwritten.
 */
static inline void list_replace(struct list_head *old, struct list_head *new)
{
    new->next = old->next;
    new->next->prev = new;
    new->prev = old->prev;
    new->prev->next = new;
}

/**
 * list_move - delete from one list and add as another's head
 * @list: the entry to move
 * @head: the head that will precede our entry
 */
static inline void list_move(struct list_head *list, struct list_head *head)
{
    __list_del_entry(list);
    list_add(list, head);
}

/**
 * list_move_tail - delete from one list and add as another's tail
 * @list: the entry to move
 * @head: the head that will follow our entry
 */
static inline void list_move_tail(struct list_head *list,
    struct list_head *head)
{
    __list_del_entry(list);
    list_add(list, head);
}

/**
 * list_is_last - tests whether @list is the last entry in list @head
 * @list: the entry to test
 * @head: the head of the list
 */
static inline int list_is_last(const struct list_head *list,
    const struct list_head *head)
{
    return list->next == head;
}

/**
 * list_empty - tests whether a list is empty
 * @head: the list to test.
 */
static inline int list_empty(const struct list_head *head)
{
    return head->next == head;
}

/**
 * list_empty_careful - tests whether a list is empty and not being modified
 * @head: the list to test
 *
 * Description:
 * tests whether a list is empty _and_ checks that no other CPU might be
 * in the process of modifying either member (next or prev)
 *
 * NOTE: using list_empty_careful() without synchronization
 * can only be safe if the only activity that can happen
 * to the list entry is list_del_init(). Eg. it cannot be used
 * if another CPU could re-list_add() it.
 */
static inline int list_empty_careful(const struct list_head *head)
{
    struct list_head *next = head->next;
    return (next == head) && (next == head->prev);
}

/**
 * list_rotate_left - rotate the list to the left
 * @head: the head of the list
 */
static inline void list_rotate_left(struct list_head *head)
{
    struct list_head *first;

    if (!list_empty(head)) {
        first = head->next;
        list_move_tail(first, head);
    }
}

/**
 * list_is_singular - tests whether a list has just one entry.
 * @head: the list to test.
 */
static inline int list_is_singular(const struct list_head *head)
{
    return !list_empty(head) && (head->next == head->prev);
}

static inline void __list_cut_position(struct list_head *list,
    struct list_head *head, struct list_head *entry)
{
    struct list_head *new_first = entry->next;

    list->next = head->next;
    list->next->prev = list;
    list->prev = entry;
    entry->next = list;
    head->next = new_first;
    new_first->prev = head;
}

static inline void __list_splice(const struct list_head *list,
    struct list_head *prev, struct list_head *next)
{
    struct list_head *first = list->next;
    struct list_head *last = list->prev;

    first->prev = prev;
    prev->next = first;

    last->next = next;
    next->prev = last;
}

/**
 * list_splice - join two lists, this is designed for stacks
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice(const struct list_head *list,
    struct list_head *head)
{
    if (!list_empty(list)) {
        __list_splice(list, head, head->next);
    }
}

/**
 * list_splice_tail - join two lists, each list being a queue
 * @list: the new list to add.
 * @head: the place to add it in the first list.
 */
static inline void list_splice_tail(struct list_head *list,
    struct list_head *head)
{
    if (!list_empty(list)) {
        __list_splice(list, head->prev, head);
    }
}

/**
 * list_entry - get the struct for this entry
 * @ptr:    the &struct list_head pointer.
 * @type:   the type of the struct this is embedded in.
 * @member: the name of the list_head within the struct.
 */
#define list_entry(ptr, type, member) container_of(ptr, type, member)

/**
 * list_first_entry - get the first element from a list
 * @ptr:    the list head to take the element from.
 * @type:   the type of the struct this is embedded in.
 * @member: the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_first_entry(ptr, type, member) \
    list_entry((ptr)->next, type, member)

/**
 * list_last_entry - get the last element from a list
 * @ptr:    the list head to take the element from.
 * @type:   the type of the struct this is embedded in.
 * @member: the name of the list_head within the struct.
 *
 * Note, that list is expected to be not empty.
 */
#define list_last_entry(ptr, type, member) list_entry((ptr)->prev, type, member)

/**
 * list_first_entry_or_null - get the first element from a list
 * @ptr:    the list head to take the element from.
 * @type:   the type of the struct this is embedded in.
 * @member: the name of the list_head within the struct.
 *
 * Note that if the list is empty, it returns NULL.
 */
#define list_first_entry_or_null(ptr, type, member) \
    ({ \
        struct list_head *head__ = (ptr); \
        struct list_head *pos__ = READ_ONCE(head__->next); \
        pos__ != head__ ? list_entry(pos__, type, member) : NULL; \
    })

/**
 * list_next_entry - get the next element in list
 * @pos:    the type * to cursor
 * @member: the name of the list_head within the struct.
 */
#define list_next_entry(pos, member) \
    list_entry((pos)->member.next, typeof(*(pos)), member)

/**
 * list_prev_entry - get the prev element in list
 * @pos:    the type * to cursor
 * @member: the name of the list_head within the struct.
 */
#define list_prev_entry(pos, member) \
    list_entry((pos)->member.prev, typeof(*(pos)), member)

/**
 * list_for_each - iterate over a list
 * @pos:    the &struct list_head to use as a loop cursor.
 * @head:   the head for your list.
 */
#define list_for_each(pos, head) \
    for ((pos) = (head)->next; (pos) != (head); (pos) = (pos)->next)

/**
 * list_for_each_prev - iterate over a list backwards
 * @pos:    the &struct list_head to use as a loop cursor.
 * @head:   the head for your list.
 */
#define list_for_each_prev(pos, head) \
    for ((pos) = (head)->prev; (pos) != (head); (pos) = (pos)->prev)

/**
 * list_for_each_safe - iterate over a list safe against removal of list entry
 * @pos:    the &struct list_head to use as a loop cursor.
 * @n:      another &struct list_head to use as temporary storage
 * @head:   the head for your list.
 */
#define list_for_each_safe(pos, n, head) \
    for ( \
        (pos) = (head)->next, (n) = (pos)->next; \
        (pos) != (head); \
        (pos) = (n), (n) = (pos)->next \
    )

/**
 * list_for_each_prev_safe - iterate over a list backwards safe against removal
 * of list entry
 * @pos:    the &struct list_head to use as a loop cursor.
 * @n:      another &struct list_head to use as temporary storage
 * @head:   the head for your list.
 */
#define list_for_each_prev_safe(pos, n, head) \
    for ( \
        (pos) = (head)->prev, (n) = (pos)->prev; \
        (pos) != (head); \
        (pos) = (n), (n) = (pos)->prev \
    )

/**
 * list_for_each_entry - iterate over list of given type
 * @pos:    the type * to use as a loop cursor.
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 */
#define list_for_each_entry(pos, head, member) \
    for ( \
        (pos) = list_first_entry(head, typeof(*(pos)), member); \
        &((pos)->member) != (head); \
        (pos) = list_next_entry(pos, member) \
    )

/**
 * list_for_each_entry_reverse - iterate backwards over list of given type.
 * @pos:    the type * to use as a loop cursor.
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 */
#define list_for_each_entry_reverse(pos, head, member) \
    for ( \
        (pos) = list_last_entry(head, typeof(*(pos)), member); \
        &((pos)->member) != (head); \
        (pos) = list_prev_entry(pos, member) \
    )

/**
 * list_prepare_entry - prepare a pos entry for use in
 * list_for_each_entry_continue()
 * @pos:    the type * to use as a start point
 * @head:   the head of the list
 * @member: the name of the list_head within the struct.
 *
 * Prepares a pos entry for use as a start point in
 * list_for_each_entry_continue().
 */
#define list_prepare_entry(pos, head, member) \
    ((pos) ?: list_entry(head, typeof(*(pos)), member))

/**
 * list_for_each_entry_continue - continue iteration over list of given type
 * @pos:    the type * to use as a loop cursor.
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Continue to iterate over list of given type, continuing after
 * the current position.
 */
#define list_for_each_entry_continue(pos, head, member) \
    for ( \
        (pos) = list_next_entry(pos, member); \
        &((pos)->member) != (head); \
        (pos) = list_next_entry(pos, member) \
    )

/**
 * list_for_each_entry_continue_reverse - iterate backwards from the given point
 * @pos:    the type * to use as a loop cursor.
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Start to iterate over list of given type backwards, continuing after
 * the current position.
 */
#define list_for_each_entry_continue_reverse(pos, head, member) \
    for ( \
        (pos) = list_prev_entry(pos, member); \
        &((pos)->member) != (head); \
        (pos) = list_prev_entry(pos, member) \
    )

/**
 * list_for_each_entry_from - iterate over list of given type from the current
 * point
 * @pos:    the type * to use as a loop cursor.
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing from current position.
 */
#define list_for_each_entry_from(pos, head, member) \
    for (; &((pos)->member) != (head); (pos) = list_next_entry(pos, member))

/**
 * list_for_each_entry_from_reverse - iterate backwards over list of given type
 *                                    from the current point
 * @pos:    the type * to use as a loop cursor.
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, continuing from current position.
 */
#define list_for_each_entry_from_reverse(pos, head, member) \
    for (; &((pos)->member) != (head); (pos) = list_prev_entry(pos, member))

/**
 * list_for_each_entry_safe - iterate over list of given type safe against
 * removal of list entry
 * @pos:    the type * to use as a loop cursor.
 * @n:      another type * to use as temporary storage
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 */
#define list_for_each_entry_safe(pos, n, head, member) \
    for ( \
        (pos) = list_first_entry(head, typeof(*(pos)), member), \
            (n) = list_next_entry(pos, member); \
        &((pos)->member) != (head); \
        (pos) = (n), (n) = list_next_entry(n, member) \
    )

/**
 * list_for_each_entry_safe_continue - continue list iteration safe against
 * removal
 * @pos:    the type * to use as a loop cursor.
 * @n:      another type * to use as temporary storage
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Iterate over list of given type, continuing after current point,
 * safe against removal of list entry.
 */
#define list_for_each_entry_safe_continue(pos, n, head, member) \
    for ( \
        (pos) = list_next_entry(pos, member), \
            (n) = list_next_entry(pos, member); \
        &((pos)->member) != (head); \
        (pos) = (n), (n) = list_next_entry(n, member) \
    )

/**
 * list_for_each_entry_safe_from - iterate over list from current point safe
 * against removal
 * @pos:    the type * to use as a loop cursor.
 * @n:      another type * to use as temporary storage
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Iterate over list of given type from current point, safe against
 * removal of list entry.
 */
#define list_for_each_entry_safe_from(pos, n, head, member) \
    for ( \
        (n) = list_next_entry(pos, member); \
        &((pos)->member) != (head); \
        (pos) = (n), (n) = list_next_entry(n, member) \
    )

/**
 * list_for_each_entry_safe_reverse - iterate backwards over list safe against
 * removal
 * @pos:    the type * to use as a loop cursor.
 * @n:      another type * to use as temporary storage
 * @head:   the head for your list.
 * @member: the name of the list_head within the struct.
 *
 * Iterate backwards over list of given type, safe against removal
 * of list entry.
 */
#define list_for_each_entry_safe_reverse(pos, n, head, member) \
    for ( \
        (pos) = list_last_entry(head, typeof(*(pos)), member), \
            (n) = list_prev_entry(pos, member); \
        &((pos)->member) != (head); \
        (pos) = (n), (n) = list_prev_entry(n, member) \
    )

/**
 * list_safe_reset_next - reset a stale list_for_each_entry_safe loop
 * @pos:    the loop cursor used in the list_for_each_entry_safe loop
 * @n:      temporary storage used in list_for_each_entry_safe
 * @member: the name of the list_head within the struct.
 *
 * list_safe_reset_next is not safe to use in general if the list may be
 * modified concurrently (eg. the lock is dropped in the loop body). An
 * exception to this is if the cursor element (pos) is pinned in the list,
 * and list_safe_reset_next is called after re-taking the lock and before
 * completing the current iteration of the loop body.
 */
#define list_safe_reset_next(pos, n, member) (n) = list_next_entry(pos, member)

#endif
